9-126 Section 915. Bridg e Coating Systems
915.01 General Requirements
Select a complete coating system from the Qualified Products List for each structure . Use the same coating system for all coating repairs to the structure including warranty work . The system must consist of a tinted organic zinc -rich primer, white intermediate coat, and urethane top coat matching the AMS-STD -595, “Colors Used in Government Procurement ,” color number shown on the plans . For faying surfaces of slip critical bolted connections, use a zinc -rich primer meeting the requirements for Class B slip coefficient. Before coating, provide the Engineer with the product data sheets showing mixing and thinning directions and the manufacturer -recommended spray nozzles and pressures for each product . Provide t he Engineer with documentation stating the date of manufacture for the coating product components. Use spray equipment to apply the coating. The coating products and the thinners must arrive at the project in new, unopened containers and remain unopened until required for use. Coating containers must be labeled with the manufacturer ’s name, product name, batch number, and date of manufacture; in addition, the top coat label must include the AMS-STD -595 color number . The label informat ion must be legible.
915.02 Mixing the Coating
Using a high shear mixer, mix the coating in accordance with the manufacturer ’s recommendations to a homogenous consistency . Do not use paddle mixers or paint shakers . Strain the primer after mixing except where spray equipment is provided with strainers . Strainers must be sized to remove undesirable material but not to remove pigment . Follow the coating manufacturer ’s recommendations for sweat -in-time/induction-time before applying the coating. Continuously agitate t he primer until application is complete.
915.03 Thinning the Coating
Do not thin the coating unless recommended by the coating manufacturer . For thinning the coating, provide thinner (s) recommended by the coating manufacturer . Store thinner(s) with other coatings in accordance with the manufacturer ’s recommendations . Thin coatings in accordance with the manufacturer ’s recommendations . Do not exceed the manufacturer ’s recommended thinning limits. MDOT Standard Specifications for Construction Section 915 9-127 915.04. Conditions for Coating Apply coatings under the conditions specified by this subsection.
A.Temperature . Do not apply coatings if air, coating material , or steel temperature is greater than 100°F or if the air, coating material , or steel temperature is less than 5°F higher than the dew point . Apply the primer and intermediate coats if air, coating material, and steel temperatures meet or exceed 50°F . Apply the top coat if air, coating material, and steel temperatures meet or exceed 40°F . Follow the coating ma nufacturer ’s recommendations for minimum and maximum temperature if more stringent . Unless the manufacturer recommends a longer recoat time, maintain the specified minimum air and steel temperatures between coats for 24 hours in the field or for 16 hours i n the fabrication shop.
B.Humidity . Do not apply coating if the relative humidity exceeds 90% or if temperature and humidity conditions cause moisture to condense on the surfaces requiring coating. Use a psychrometer to measure the humidity . Follow the coati ng manufacturer ’s recommendations for minimum and maximum humidity if more stringent .
C.Heating . If heating is required, heaters must maintain air and steel temperatures from 50 to 100°F without discharging oils or other pollutants into the enclosure.
D.Storag e and Shelf Life of Coating . Store the coating materials in original unopened containers in weathertight areas where the temperature is maintained between 40 and 100°F unless otherwise recommended in writing by the coating manufacturer . Use coating within the stated shelf life indicated for each component of the coating on its technical/ product data sheets.
Source: Michigan Standard Specifications for Construction, 2020 Edition. Pages 936–937 of 1,146.